pub fn dp_rec_mc(amount: u32) -> u32 {
    // 定义纸币种类
    let coins = [1, 2, 5, 10, 20, 30, 50, 100];
    // 初始化 dp 数组，长度为 amount + 1，初始值为无穷大
    let mut dp = vec![u32::MAX; (amount + 1) as usize];
    dp[0] = 0; // 0 元需要 0 张纸币

    // 填充 dp 数组
    for &coin in &coins {
        for i in coin..=amount {
            if dp[(i - coin) as usize] != u32::MAX {
                dp[i as usize] = dp[i as usize].min(dp[(i - coin) as usize] + 1);
            }
        }
    }

    // 返回结果
    dp[amount as usize]
}